As known, both commercial and military aircraft use bleed air from the aircraft's gas turbine engine to supply pneumatic and thermal energy to on board systems which provide aircraft air conditioning, cabin pressurization, thermal anti-ice (TAI), and engine thrust reversal.
The warm compressed bleed air supplied to the TAI system is used to de-ice and/or prevent the accumulation of ice on the leading edge of the engine cowlings and the leading edges of the aircraft wing. Since the bleed air taken from the engine to supply the TAI system is compressed air that can not be used for thrust, the TAI system should be designed to be as judicious as possible with respect to the amount of bleed air it takes from the engine. This often leads to aggressive designs and control systems to ensure that only the necessary amount of bleed air is taken, and therefore engine efficiency remains high which leads to reduced engine operating costs.
Since the TAI system should use a minimum amount of necessary bleed air to perform the anti-ice function, the operating line of the TAI control system must be aggressively designed in order to extract only the minimum amount of bleed air. While various regulating valve designs have been proposed for the TAI control system, for the most part, such valve designs have exhibited less than optimum control stability.